@caterpillar5 Side note - depending on the country you’re in, she may not get any choice anyway - the UK wouldn’t let under 16s in the venue without an adult anyway.
@caterpillar5 It's not up for debate. How or why her friend is asking you to pass your ticket to her instead is definitely rude. But do you think she's acting alone? Do you suspect that your daughter may have suggested that she text you because it's strange that she would be so brazen on her own, especially given the context. And the fact that your daughter is also asking her to pass it along to her 'bestie' makes that seem plausible. If they're conspiring on how to pry that ticket from your hands, I'd really consider going with your sister. You don't want to be punitive but you still have to be assertive enough so that they both know that they need to drop the notion that somehow they will be going to the concert together.